Explaining Inheritance but different

Gene

A segment of DNA that codes for a protein or trait.

Allele

Different versions of the same gene.

Gene Locus

The specific position or location of a gene on a chromosome

Maternal Chromosome

Chromosome inherited from the mother.

Paternal Chromosome

Chromosome inherited from the father.

Genotype

The genetic makeup (allele combination) of an organism., displayed in letters, e.g. AA/Aa/aa

Phenotype

The physical traits expressed by the genotype.

Dominant Allele

An allele whose trait is expressed in the phenotype even when present in a single copy.

Recessive Allele

An allele only expressed when two copies are present.

Homozygous

Having two identical alleles for a gene.

Heterozygous

Having two different alleles for a gene.

Co-Dominance

When both alleles at a locus contribute independently and visibly to the phenotype (e.g., blood type AB)

Incomplete Dominance

When neither allele is completely dominant; the heterozygous phenotype is intermediate or blended

Complete Dominance

One allele completely masks the other.

Ploygenetic

Traits controlled by multiple genes (e.g., height, skin color).

Monogenetic

Traits controlled by a single gene.

Epigentics

Changes in gene expression without changing DNA sequence.

Sex-Linked Genotypes

Genotypes involving genes on the X or Y chromosomes.

X Chromosome

The larger sex chromosome; carries many genes.

Y Chromosome

The smaller sex chromosome; carries genes for male sex traits.

Monohybrid Cross

A genetic cross examining one trait.

Punnett Square

A diagram showing possible offspring genotypes.

Genotypic Ratio

Ratio of different genotypes from a cross (e.g., 1:2:1).

Phenotypic Ratio

Ratio of different phenotypes from a cross (e.g., 3:1).

Autosomal Complete Dominance

Trait on autosome where dominant allele fully masks recessive (e.g., brown vs blue eyes).

Autosomal Incomplete Dominance

Trait on autosome showing blended phenotype (e.g., red + white flowers = pink).

Autosomal Co-Dominance

Trait on autosome where both alleles are fully expressed (e.g., blood type AB).

Sex-Linked Alleles

Traits carried on sex chromosomes (e.g., hemophilia on X chromosome).

Test Cross

Cross between unknown genotype and homozygous recessive to determine genotype.

Pedigree Chart

A family tree diagram showing inheritance of traits.

Generation

Each row in pedigree; labelled with Roman numerals (I, II, III).

Unaffected Male

Empty square (□).

Unaffected Female

Empty circle (○).

Affected Male

Shaded square (■).

Affected Female

Shaded circle (●).

Consanguineous Breeding

Mating between relatives (double horizontal line in pedigree).

Autosomal Dominant

Trait appears in every generation; both sexes equally affected.

Autosomal Recessive

Trait can skip generations; both sexes equally affected.

X-Linked Dominant

More females affected; affected fathers pass to all daughters.

X-Linked Recessive

More males affected; often skips generations; females carriers.

Y-Linked

Only males affected; passed from father to all sons.